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Density fluctuations of a clot of aerosol particles in the atmosphere are studied. A one-dimensional case is considered characteristic of the motion of particles in a narrow vertical fire column or in an aircraft trail. The effect of localization of clots is shown to be observed under certain conditions, which consists in the formation of compact areas of high density of aerosol particles surrounded by areas of low density. Knowledge of such properties of impurity density can be useful in solving inverse problems of aerosol optics. [ABSTRACT FROM AUTHOR]

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The mechanisms affecting plasma by external and internal inputs must be understood for both semiconductor processing and controlled nuclear fusion, which require stable and steady-state plasmas. Among various factors that can change the state of plasma, detecting and controlling the plasma–wall interactions inside the reactor are challenging. In particular, although water is a commonly encountered impurity in most vacuum systems including process chambers, studies on the direct evidence of water effect on plasma are limited. Herein, we show that there is a clear negative correlation between the impurity density and the plasma density. A small change in water impurity could cause an immediate change in the plasma density because impurities contribute to increasing the total energy loss in the steady-state plasma sustainment. To observe the impurity effect distinctly, we conducted experiments under various conditions to analyze the effect of vessel impurities on plasma parameters, such as applied power, wall contamination, and wall materials. In the experiments, it is found that the plasma density is significantly influenced by the impurity density. The results were compared with the global model calculation and they are in agreement on the relative change of the electron density. • Influence of impurity on inductively coupled plasma is analyzed. • Introduction of impurities with high rate constants decreases the electron density. • Simulation shows 0.1% H 2 O/Ar flowrate ratio lowers electron density by 74%. • Discharge cleaning effectively reduces impurity content in the vacuum vessel. • Impurity content in the vessel depends on wall material characteristics. [ABSTRACT FROM AUTHOR]

A number of workers have shown that the vapor pressure of the reactant gases strongly influences the electrical properties of GaAs vapor grown in the ASCI system. This paper presents the results of a study of the effects of the variation of vapor pressures on GaAsP grown in the hydride synthesis system. The material was analyzed using Hall effect measurements taken as a function of temperature from room to liquid helium temperatures, and using test electroluminescent diodes. A least squares fit was made to the Hall effect data using a model which includes the effects of two valley conduction to obtain densities of donors and acceptors and donor ionization energies. Increasing reactant gas pressure causes a decrease in donor and acceptor densities as N, N∞ P -2.5 which is slower than the P observed by DiLorenzo in the ASCI system. The ionization energy of the donors was quite high (100 meV) for the high and low pressures, and were less than 10 meV for the intermediate pressures. Hall mobilities at room and liquid nitrogen temperatures were best for material grown at intermediate pressures and the electroluminescent efficiencies of unencapsulated test diodes increased from 0.05 per cent at the extremes to above 0.1-0.2 per cent at the intermediate pressures. These variations are consistent with varying Si incorporation rate and varying density of point defects with varying reactant gas vapor pressure. [ABSTRACT FROM AUTHOR]

• Electron-spin relaxation times in 3D and 2D p-type GaAs were discussed. • Concentrations of deep and show impurities were calculated for prolonged electron spin relaxation times. • The concentration of shallow donors needs to exceed the concentration of the shallow acceptor. • The maximum spin relaxation times for the 2D and 3D materials are 77 ns and 154 ns, respectively. Magnetic semiconductors have aroused interest due to their various functionalities related to spintronic devices. Manganese (Mn) as a substitutional impurity in A 3 B 5 semiconductors supplies not only holes, but also localized spins. The ejection of Mn atoms with an uncompensated magnetic moment leads to the appearance of ferromagnetic properties. The most suitable material characterized by long-term spin dynamics is n-type GaAs. In p-type GaAs, the spin relaxation time of electrons is generally much shorter. For purposes of this research, electron-spin relaxation times in 3D and 2D p-type GaAs were studied. Calculation of impurity densities and charge state of magnetic acceptors demonstrate the essential composition of the material. Comparison of theoretical and experimental data in optical-spin orientation of electrons reveal the longest spin relaxation time of 77 ns in 2D GaAs:Mn, less than twice the best time in the p-type 3D GaAs material. [ABSTRACT FROM AUTHOR]